Polymeric balls or polymeric beads both doped with metal elements may be made and this up to now according to two major synthesis routes.
According to a first route, polymeric balls or beads synthesized beforehand are immersed in a solution comprising the metal element, said metal element diffusing by physical impregnation through the wall of the ball in order to occupy the central cavity of the microball or through the wall of the bead in order to occupy the porosity of the latter. At the end of this physical impregnation, balls are thus found having an excess of metal element in the central cavity relatively to the amount of metal element present in the wall or an excess of metal element in certain areas of the beads and with an impossibility of controlling the amount of this metal element inside said wall or said beads.
In order to remove the metal element excess in the central cavity of the balls, one solution consists of having the thereby doped balls undergo a washing step with a solvent capable of being exchanged with the one present in the central cavity and thereby discharging concomitantly the metal element present in said cavity. However, this washing step is not discriminating and will also remove a large portion or even the totality of the metal element present inside the wall of the balls.
The same problems are posed as regards the beads when the question is of discharging the excess metal element in certain porous areas of the beads.
The consequence is therefore that it is very difficult to proceed with doping of balls or beads synthesized beforehand with metal elements and with monitoring the doping level of the latter.
In order to overcome the aforementioned drawbacks, certain authors have explored a second synthesis route, as regards manufacturing of balls, which consists in a method comprising the following steps:                a step for machining half-shells in a foam block, the half-shells being capable from a geometrical point of view, of being joined together by adhesive bonding so as to form a ball;        a step for impregnating the half-shells with a solution comprising a metal salt;        a step for drying the thereby impregnated half-shells, by means of which the consequence is a deposit of metal salt in the constitutive polymer of the half-shells;        a step for adhesively bonding the half-shells in order to form a ball.        
However, this synthesis route proves to be complex to apply and with it, balls having good sphericity may be obtained with difficulty.
Thus, from the routes for synthesizing doped balls or doped beads with metal elements of the prior art, one or several of the following drawbacks emerge:                for the first method explained above:        an inability to control the level of doping with metal elements in the constitutive walls of the balls or beads;        an accumulation of metal elements in the central cavity of the balls or in the porosity of the beads, for which the only removal route is by washing which is inevitably accompanied by removal of the metal element from the constitutive walls of the balls or beads; and        for the second method explained above:        very complex manufacturing when the question is of manufacturing balls by machining half-shells and assembling the latter.        
The inventors thus set their goal of proposing a method for producing doped polymeric balls or doped polymeric beads not having the aforementioned drawbacks.